The present invention relates to x-ray imaging, and more particularly, to suppressing bone structures based on a single x-ray image.
Chest radiography (i.e., x-ray imaging) is a frequently used imaging technique for the diagnosis of chest diseases, such as lung cancer, pneumoconiosis, and pulmonary emphysema. However, it is difficult to detect lung nodules (i.e., potential lung cancers) in a conventional chest radiograph (x-ray image) because lung nodules are often obscured in chest radiographs by overlying bones, such as ribs and clavicles. Even with a computer-aided diagnostic (CAD) scheme for nodule detection, it can be challenging to detect nodules in chest radiographs when bones overlap with the nodules.
A conventional solution to this problem is to use dual energy imaging in order to separate a chest radiograph into a bone image and a soft-tissue image. FIG. 1 illustrates dual energy imaging. As illustrated in FIG. 1, images 102 and 104 are dual energy images. In dual energy imaging, in addition to normal exposure for a standard radiograph, a patient receives extra x-ray exposure at a lower energy to acquire a second radiograph, resulting in a high-energy x-ray image and a low-energy x-ray image. In FIG. 1, image 102 is the high-energy image and image 104 is the low-energy image. A sensor array is used to capture the x-rays that transverse through the patient. Since the attenuation coefficients of bone and soft tissue follow different functions of energy, the two images can be weighted and then subtracted to generate separate images for soft tissue and bone structure. In FIG. 1, image 106 is a bone image and image 108 is a soft-tissue image.
Despite the advantages of dual energy imaging, many hospitals do not use dual energy imaging because specialized equipment is required. Also, dual energy imaging requires extra x-ray exposure for patients, such that the radiation dose can be greater than the recommended amount for obtaining standard radiographs. Accordingly, a method for suppressing bone structures in an x-ray image without using dual energy imaging is desirable.